Identifying conserved molecular targets required for cell migration of glioblastoma cancer stem cells

Josephine Volovetz,Jocelyn A Mcdonald,Yujun Chen,Ashley Burtscher,George F Aranjuez,John Peterson,Daniel J Silver,Justin D Lathia,Danny Manor,Adam Lauko,Tyler Alban,Kelly Shibuya,Artem D Berezovsky

doi:10.1038/s41419-020-2342-2

Abstract

Glioblastoma (GBM) is the most prevalent primary malignant brain tumor and is associated with extensive tumor cell infiltration into the adjacent brain parenchyma. However, there are limited targeted therapies that address this disease hallmark. While the invasive capacity of self-renewing cancer stem cells (CSCs) and their non-CSC progeny has been investigated, the mode(s) of migration used by CSCs during invasion is currently unknown. Here we used time-lapse microscopy to evaluate the migratory behavior of CSCs, with a focus on identifying key regulators of migration. A head-to-head migration assay demonstrated that CSCs are more invasive than non-CSCs. Time-lapse live cell imaging further revealed that GBM patient-derived CSC models either migrate in a collective manner or in a single cell fashion. To uncover conserved molecular regulators responsible for collective cell invasion, we utilized the genetically tractable Drosophila border cell collective migration model. Candidates for functional studies were generated using results from a targeted Drosophila genetic screen followed by gene expression analysis of the human homologs in GBM tumors and associated GBM patient prognosis. This strategy identified the highly conserved small GTPase, Rap1a, as a potential regulator of cell invasion. Alteration of Rap1a activity impaired the forward progress of Drosophila border cells during development. Rap1a expression was elevated in GBM and associated with higher tumor grade. Functionally, the levels of activated Rap1a impacted CSC migration speed out of spheres onto extracellular matrix. The data presented here demonstrate that CSCs are more invasive than non-CSCs, are capable of both collective and single cell migration, and express conserved genes that are required for migration and invasion. Using this integrated approach, we identified a new role for Rap1a in the migration of GBM CSCs.

Highlights

Glioblastoma (GBM), the most prevalent primary malignant brain tumor in adults, remains one of the most lethal cancers, with a median survival of less than 2 years[1,2,3,4]
cancer stem cells (CSCs) are more invasive than non-CSCs Previous studies suggest CSCs have increased migration and invasion capacity compared to non-CSCs
CSCs exhibited 2- to 5-fold increase in migration versus nonCSCs. These results demonstrate that CSCs are more invasive than non-CSCs when compared in identical conditions

Summary

Introduction

Glioblastoma (GBM), the most prevalent primary malignant brain tumor in adults, remains one of the most lethal cancers, with a median survival of less than 2 years[1,2,3,4]. A number of pathways drive GBM cell invasion, such as the Wingless/Int[1] (Wnt) and TGF-β pathways[10]. Official journal of the Cell Death Differentiation Association. Volovetz et al Cell Death and Disease (2020)11:152 mechanisms are associated with self-renewal[11], the extent to which they drive invasion over self-renewal has yet to be determined. Studies in the perivascular environment revealed that cells migrate faster and induce further microvascular development[15,16]. These observations suggest that invasion itself may contribute to therapeutic resistance in GBM

Methods

Results

Conclusion